Stabilized hypohalous acid solutions

ABSTRACT

The present invention provides a stabilized hypohalous acid solution (or formulation thereof), which may be conveniently packaged for sale, or stored for later use on demand. The invention further provides methods of making the stabilized hypohalous acid solution, as well as methods of use for disinfecting mammalian tissue, including wounds and burns, disinfecting or cleansing surfaces, or treating and/or preserving food products and cut flowers, among other uses.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/018,306 filed Jun. 26, 2018, which is a continuation of U.S.patent application Ser. No. 15/184,207 filed Jun. 16, 2016 (U.S. Pat.No. 10,034,942), which is a continuation of U.S. patent application Ser.No. 14/501,977 filed Sep. 30, 2014 (U.S. Pat. No. 9,392,787), which is acontinuation of U.S. patent application Ser. No. 13/423,822 filed Mar.19, 2012 (U.S. Pat. No. 8,871,278), which claims the benefit of andpriority to U.S. Provisional Application No. 61/454,383, filed Mar. 18,2011, and U.S. Provisional Application No. 61/526,149, filed Aug. 22,2011, each of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to stabilized solutions and formulationsof hypohalous acid, such as hypochlorous acid (HOCl), as well as methodsfor their production and use. The solution finds use for cleaning and/ordisinfecting surfaces, food such as fruit, vegetables and crops, ormammalian tissues (including wounds). The solutions further find use inthe preservation of agricultural products and cut flowers.

BACKGROUND

Hypochlorous acid is an oxidant and biocide that is produced by thehuman body's natural immune system to fight infection. Hypochlorous acidis generated as the final step of the Oxidative Burst Pathway, withlarge quantities of hypochlorous acid being released into the phagocyticvesicles to destroy the invading microorganisms. It is considered thathypochlorous acid exerts its biocidal effect by attacking the surfaceand plasma membrane proteins, impairing transport of solutes and thesalt balance of bacterial cells (Pieterson et al., Water SA, 22(1):43-48 (1996)). Escherichia coli exposed to hypochlorous acid loseviability in less than 100 ms due to inactivation of many vital systems.(Fair et al., 40 J. Am. Water Works Assoc. 1051-61 (1940)). Hypochlorousacid at 2.6 ppm caused 100% growth inhibition of E. coli in dilutebacterial suspensions in about 5 minutes. (Chesney et al., 178 J.Bacteria 2131-2135 (1996)). According to Chemistry of Water Treatment(2^(nd) Edition), S. D. Faust and O. M. Aly (1998), 100% kill in 5minutes requires only 0.08 ppm for A. aerogenes, 0.06 ppm for S.typhosa, 0.05 ppm for S. dysenteriae, and 0.03 ppm for E. coli.

Although hypochlorous acid is biocidal for microorganisms, it is notsignificantly toxic to human or animal cells, at least partly becausehuman and animal cells have extensive, highly effective defensemechanisms known as the Antioxidant Defense System (ADS).

Hypohalous acid has a wide range of applications where it is importantto control microbial contamination, such as for the care and managementof wounds, disinfecting hard surfaces such as medical or dentalequipment, food safety and processing, water treatment, as well as otherindustrial and agricultural applications.

One limitation associated with solutions of hypochlorous acid is theirstability, which has limited much of the commercial use to thosesituations where the solution can be made on site for relativelyimmediate use. Existing alternatives include Dakin's solution for woundcare, which is a diluted sodium hypochlorite solution (0.5%) prepared bymixing sodium hypochlorite (5.25%), sodium bicarbonate/carbonate (1%),and clean tap water. However, Dakin's solution has a high pH, and thuscauses pain and burning in wound treatment along with rashes, itching,swelling, hives, and/or blisters. Further, Dakin's solution is unstableand unsuited for clinical use at lower pH's (<8.5). Another alternativeis the Microcyn™ solution. While Microcyn has a 2 year shelf life, itsuffers from a limited level of available free chlorine (AFC) of about80 ppm (pH of 7.4), and lower percent of hypochlorous acid, which maylimit its biocidal effectiveness. EcaFlo™ is available for hard surfacedisinfection. This solution contains equimolar amounts of hypochloriteand hypochlorous acid in addition to high sodium chloride content. ThepH of the solution is around 7.5 and the solution has an AFC content ofapproximately 460 ppm. The solution has a relatively short shelf life of30 days.

There is an unmet need for a hypohalous acid solution that has a highAFC content, has sufficient stability and/or other properties requiredto be commercially useful in medical and other commercial settings, andis not irritating or harmful to humans. The claimed invention meetsthese and other objectives.

SUMMARY OF THE INVENTION

The present invention provides a stabilized hypohalous acid solution orformulation thereof, which may be conveniently packaged for sale, orstored for later use on demand. The invention further provides methodsof making the stabilized hypohalous acid solution or formulationthereof, as well as methods of use for disinfecting mammalian tissue,including wounds and burns, disinfecting or cleansing hard surfaces,treating (e.g., preserving and/or disinfecting) food products or cutflowers, among other uses.

In one aspect, the invention provides a stabilized hypohalous acidsolution, which can be a hypochlorous acid solution or a hypobromousacid solution for example. The solution incorporates a stabilizingamount of dissolved inorganic carbon (DIC), which can be in the form ofa bicarbonate or carbonate of an alkali or alkaline earth metal. Thesolution may have an available free chlorine (AFC) content of from about10 to about 10,000 parts per million, and a pH of from about 4.0 toabout 7.5. For example, in certain embodiments, the solution has a pH offrom about 5 to about 7. In certain embodiments, the solution containshypochlorous acid, and is prepared by electrolysis of saline. Thesolution is stabilized, as determined by its change in pH and/or AFCover time, for at least one month, but in various embodiments, thesolution is stabilized for at least six months, at least one year, ormore.

In certain embodiments, sodium bicarbonate is incorporated into thesolution at a level of about 5:1 to about 1:5 molar ratio relative tothe AFC content. For example, sodium bicarbonate may be added at a levelof about 1:1, about 1:2, or about 1:3 or at a larger (i.e., more dilute)molar ratio relative to the AFC content (e.g., the hypohalous acidcontent). In certain embodiment, sodium bicarbonate is incorporated intothe solution at a level of about 1:1 to about 1:2, relative to the AFCcontent. While the solution may contain phosphate buffers in someembodiments, in other embodiments, the solution does not contain, orcontains only limited, phosphate buffer. For example, the solution maycomprise HOCl produced by electrolysis of saline, and the solution mayhave an AFC content of from about 100 to about 500 parts per million, apH in the range of about 5 to about 7, a salinity of about 0.02% toabout 1.0%, and an amount of dissolved inorganic carbon in the range ofabout 300 mg/L to about 1500 mg/L. In some embodiments, the salinity ofthe solution does not impact the amount of bicarbonate needed forsolution stabilization. In certain embodiments, the HOCl solution isformulated as a hydrogel.

In another aspect, the invention provides a method for preparing thestabilized hypohalous acid solution. The method involves incorporatingthe DIC (e.g., in the form of carbonate or bicarbonate) by addition toan electrolyte for electrochemical treatment, or incorporating the DIC(e.g., in the form of carbonate or bicarbonate) by directly adding to anelectrolyzed solution comprising hypohalous acid (e.g., HOCl).

Still other aspects of the invention provide methods of disinfecting,cleansing, or treating a mammalian tissue, such as a wound, burn, ordermatosis, or provides methods of sanitizing, disinfecting or cleansinga hard surface, or provides methods for treating or preserving a food oragricultural product or cut flowers. Due to the stability of thehypohalous acid solutions and formulations, such methods need not beperformed proximately to the production of the biocidal solution.Further, as shown herein, stabilized hypohalous acid solutions of theinvention maintain activity even in the presence of high organic load.In still other embodiments, the invention provides a method for treatinga skin condition, including dermatosis, rosasea, skin infection, skinallergy, psoriasis, or acne. In such embodiments, the HOCl may beformulated as a hydrogel.

Other aspects of the invention will be apparent from the followingdetailed description of the invention.

DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B show the change in pH over time of an HOCl solutionstored at room temperature (FIG. 1A) or stored at less than 20° C. (FIG.1B).

FIGS. 2A and 2B show the change in AFC over time of an HOCl solutionstored at room temperature (FIG. 2A) or stored at less than 20° C. (FIG.2B).

FIG. 3 shows the AFC drop over storage time in bottled HOCl solutionscontaining bicarbonate (“non-buffered”), or with bicarbonate andphosphate buffer.

FIG. 4 shows the change in pH and AFC of the bicarbonate-containing HOClsolutions without phosphate buffer.

FIG. 5 shows the reduction in C. difficile spores in the presence ofhigh organic load. The solutions tested are as follows: pH 6.7, AFC of250 ppm, NaHCO₃ at 400 mg/L; pH 6.7, AFC of 480 mg/L, 0.0 NaHCO₃; and pH6.3, AFC of 480 ppm, and NaHCO₃ at 1000 mg/L.

FIG. 6 shows the results of an extended stability study of HOCl producedby electrochemical treatment of NaHCO₃-enriched NaCl solution attargeted pH 5.4, bottled in a polyethylene terephthalate (PET) containerand stored at room temperature.

FIGS. 7A and 7B show the stability of HOCl added to containerscomprising dry sodium bicarbonate. FIG. 7A shows stability of pH. FIG.7B shows stability of AFC content.

FIG. 8 shows the effect of bicarbonate on pH and solution stability inhypochlorous acid solutions having a targeted pH for agriculturalapplications.

FIG. 9 shows a shift in pH upon formulation as a hydrogel.

DETAILED DESCRIPTION

The present invention provides a stabilized hypohalous acid solution orformulation thereof, which may be conveniently packaged for sale, orstored for later use on demand. The invention further provides methodsof making the stabilized hypohalous acid solution, as well as methods ofuse for disinfecting mammalian tissue, including wounds and burns,disinfecting or cleansing surfaces, or treating or preserving foodproducts or cut flowers, among other uses.

In one aspect, the invention provides a stabilized hypohalous acidsolution or formulation thereof, which can be a hypochlorous acidsolution or formulation or a hypobromous acid solution or formulation,for example. The solution incorporates a stabilizing amount of dissolvedinorganic carbon (DIC), such as a bicarbonate or carbonate of an alkalior alkaline earth metal. The solution may have an available freechlorine (AFC) content of from about 10 to about 10,000 parts permillion, and a pH of from about 4.0 to about 7.5. In certainembodiments, the solution contains hypochlorous acid, and is prepared byelectrolysis of saline. The solution is stabilized, as determined by itschange in pH and/or AFC over time, for at least one month, but invarious embodiments, the solution is stabilized for at least six months,at least one year, or more.

The hypohalous acid solution may be generated by electrolysis of ahalide salt, such as chloride salt (e.g., sodium chloride) or a bromidesalt, and may comprise a mixture of oxidizing species such as, e.g.,predominantly hypochlorous acid and sodium hypochlorite, or hypobromousacid and sodium hypobromite. Hypochlorous acid and hypochlorite (orhypobromous acid and hypobromite) are in equilibrium and the position ofthe equilibrium is determined predominately by the pH (that is, pHeffects the concentration of each component). An electrolyzed sodiumchloride solution with a pH of 5.1 to 6.0 has a purity of about ≥95%hypochlorous acid. Thus, the electrolyzed solution supplied may have apH of from about 4.0 to about 7.5, but in certain embodiments has a pHof from about 4.4 to about 7.0, or a pH of about 5 to about 7, or a pHof from about 5.4 to about 6.4, or a pH of from about 5.0 to about 6.4.At a pH of about 5.4 the solution will contain mostly (close to 100%)hypochlorous acid with respect to hypochlorite.

While the solution may comprise, or consist essentially of hypochlorousacid as the active agent, in some embodiments, it may contain otherhypohalous acids (e.g., HOBr, or mixture thereof). In some embodiments,the solution contains other oxidizing or radical producing species suchas a hypohalite (e.g., hypochlorite), hydroxide, H₂O₂ and O₃, amongothers. The present invention relates to stabilized hypohalous acids,such as hypochlorous acid or hypobromous acid. While the specificationrefers to Available Free Chlorine when referring to the concentration ofthe hypohalous acid (for convenience), a person of skill in the artunderstands that, in the case of hypobromous acid, the hypohalous acidconcentration can be referred to as AFB (available free bromine).

The biocidal activity of the solution can be expressed in terms ofavailable free chlorine or AFC. While the invention is applicable to anAFC range of from about 10 to about 10,000 ppm (or to about 5000 ppm),in certain embodiments, the solution has a relatively high AFC contentand is suitable for use with mammalian tissues or agricultural products.For example, the solution may have an AFC content of from about 100 to1000 ppm, or 100 to 500 ppm, or about 150 to about 250 ppm. Other AFClevels may be employed, and may be selected based upon the intendedapplication. For example, without any limitation, for surfacedisinfection the AFC may be in the range of about 140 to about 2000 ppm,or about 400 to about 1000 ppm.

While the hypochlorous acid may be produced chemically in accordancewith some embodiments (e.g., by acidification of hypochlorite), thehypohalous acid may also be produced electrochemically. Theelectrochemical production of hypohalous acid is by treatment ofhalide-based electrolytes in a diaphragm-type electrolytic cell.Electrochemical treatment of saline is described, for example, in U.S.Pat. Nos. 7,303,660, 7,828,942, and 7,897,023, which are herebyincorporated by reference in their entireties.

The solution employs a stabilizing amount of DIC, which may be abicarbonate or carbonate of alkali or alkaline earth metal, such as, forexample, sodium, potassium, calcium, or magnesium. In some embodiments,the bicarbonates or carbonates are added prior to the formation ofhypohalous acid (e.g., by electrochemical treatment), and in otherembodiments, the bicarbonates or carbonates are added to the solutionafter formation of hypohalous acid. For example, the bicarbonate(s) orcarbonate(s) may be added to the precursor solution, the electrolyte,and/or the end solution.

The DIC is incorporated at a “stabilizing amount,” which can bedetermined with reference to the change in the pH or AFC content of thesolution over time. Generally, the solution is considered stabilized ifthe amount of AFC does not drop below about 75% of the initial valueover a period of about 6 months. In certain embodiments, the AFC contentis stabilized for at least one year from the production date of thesolution. Further, the stability of the solution may be determined withreference to the pH. Generally, the solution is considered stabilized ifthe pH does not vary by 1 unit over a period of about 6 months. Incertain embodiments, the pH is stabilized for at least one year from theproduction date of the solution. The solution should be stored at 25° C.or at 20° C. or less for greater stability. 25° C. and 20° C. are thereference temperatures for determination of stability. For stabilitytesting, solutions are packaged in HDPE bottles, stored in the dark, andkept unopened.

The stabilizing amount of DIC (e.g. as added carbonate or bicarbonate)can be determined with reference to the AFC content. For example, incertain embodiments, the stabilizing amount of the carbonate orbicarbonate is incorporated into the solution at a molar ratio of fromabout 5:1 to 1:5 with respect to the AFC level. In some embodiments, thebicarbonates or carbonates are incorporated into the solution in atleast equimolar amounts with respect to the AFC content (e.g.,hypochlorous acid content). In still other embodiments, the DIC (e.g.,bicarbonate or carbonate) is incorporated at about 5:1, about 2:1, about1:1, about 1:2, about 1:3, or about 1:5 with respect to AFC content. Invarious embodiments, other buffering components such as phosphatebuffers, are not employed, or are minimally employed. For example, forsolutions having an AFC content of from about 200 ppm to about 500 ppm,carbonate or bicarbonate may be incorporated at an amount of from about300 mg/L to about 1500 mg/L to stabilize the solution. In certainembodiments, such solutions are stabilized by incorporating from about400 to about 1000 mg/L of carbonate or bicarbonate.

Without being bound by theory, dissolved inorganic carbon (DIC), whichgenerally includes carbonates, bicarbonates, carbonic acid and dissolvedCO₂, provides low or minimal buffering capacity in the pH range targetedby the solutions and compositions described herein. Nevertheless, thesesolutions are effectively stabilized, such that the solutions andcompositions are not dependent on “on-demand” production. Thestabilizing effect can be due to, in-part, free radical scavengingability of DIC to thereby slow the decomposition of HOCl. Further still,solutions prepared by electrochemical treatment of bicarbonate-enrichedsodium chloride solution (as opposed to chemical acidification of sodiumhypochlorite stabilized with equal amount of carbonate/bicarbonate),have distinct properties with respect to DIC, and the stabilizing effectcan be distinct.

In some embodiments, as shown in FIG. 5, the addition of thebicarbonates or carbonates of alkali or alkaline earth metals providesenhanced biocidal effectiveness for treating microorganism or biofilms,especially in the presence of high organic load.

While the hypohalous acid solution may be in the form of a liquid, thesolution may take the form of a cream, gel (e.g. silicon-based gel),and/or foam by the addition of conventional ingredients known in theart. For example, topical formulations of electrochemical solutions aredisclosed in US 2005/0196462, which is hereby incorporated by referencein its entirety. In these embodiments, the formulation is bettercontained around the application site by limiting solution run-off.Further, convenient applicators for creams, foams, and the like areknown, and may be used in accordance with the present invention. Sincethe solutions of the invention provide the potential for lowconductivity, even with relatively high AFC content, and at“skin-friendly” pH levels, the solutions of the invention areparticularly suitable for hydrogel formulations.

In certain embodiments employing hydrogel formulations, the compositionhas an AFC content of greater than about 100 ppm, greater than about 150ppm, greater than about 200 ppm, greater than about 250 ppm, or greaterthan about 300 ppm. Further, the formulation may have a viscosity offrom about 0.5 mS/cm to about 12 mS/cm, such as from about 1 mS/cm toabout 10 mS/cm in some embodiments. Further, hydrogel formulations insome embodiments have a pH of from about 5 to about 7, or from about 5to about 6.5 in other embodiments. The hydrogels may be prepared fromsilicate-based carriers, such as sodium magnesium fluorosilicate (e.g.,from about 0.5% to about 5%), and may employ an additional buffer fortargeting the pH. An exemplary buffer is phosphoric acid.

The stabilized solutions may be packaged for storage or sale, using anysuitable container, such as any suitable plastic or glass bottles, orbags (e.g., plastic bags), tubes, or cans (e.g., spray or aerosol). Incertain embodiments, the packaging material has minimal gaspermeability, including by species such as CO₂ and 02. The containersmay be transparent, or opaque so that they are impenetrable by light,and may be of any unit volume, such as about 100 ml, about 125 ml, about250 ml, about 0.5 liter, about 1 liter, about 5 liters, about 10 liters,or greater.

The hypochlorous acid solution of the invention may also be hypertonic,hypotonic, or isotonic with respect to physiological fluids (blood,plasma, tears, etc.). Alternatively, the solution may contain varyinglevels of salinity, such as from 0.01 to about 2.0%. Generally, thesolution contains from about 0.02% to about 0.9% w/v NaCl when intendedfor use in medicine. In some embodiments, the solution may be a normalsaline solution (about 0.9% w/v NaCl). In some embodiments, the solutionmay contain from about 0.01 to 2.0% w/v one or more salts, such as ahalide salt, e.g. NaCl, KCl, or a mixture of salts or halide salts. Thesalt, or halide salt may be a salt of an alkali metal or alkaline earthmetal, such as sodium, potassium, calcium, or magnesium. In certainembodiments, the electrolyzed solution is generated using a mixture ofphysiologically balanced salts, as disclosed in U.S. Pat. No. 6,426,066,which is hereby incorporated by reference in its entirety. Such saltsmay include potassium halides (e.g., KCl) and magnesium halides (e.g.,MgCl₂).

In another aspect, the invention provides a method for preparing thestabilized hypohalous acid solution. The method involves incorporatingthe carbonate or bicarbonate into an electrolyte for electrochemicaltreatment, or directly to an electrolyzed solution comprising hypohalousacid (e.g., HOCl).

For example, an electrolyzed solution or other hypohalous acid solutionmay be diluted with water or aqueous solution comprising bicarbonates orcarbonates. In other embodiments, the diluted hypohalous acid solution(e.g., having the desired AFC content) is added to containers comprisingdry bicarbonates or carbonates of alkali or alkaline earth metals. Thelatter is an effective method for production of low ionic strengthhypohalous acid solutions, especially for hydrogel formulations.

The stabilized hypochlorous acid solutions (e.g. solutions of greaterthan 90%, 95%, or 97% HOCl) may be obtained by electrolysis of a salinesolution as described in U.S. Pat. No. 7,276,255, which is herebyincorporated by reference in its entirety, or can be prepared by anysuitable method or apparatus, by incorporating the bicarbonate orcarbonate into the dry electrolyte or the solution for electrolysis. Thecarbonate or bicarbonate can be added to the dry electrolyte inaccordance with the desired AFC content of the resulting solution, asdescribed in detail herein. Hypochlorous acid solutions may be preparedby passing saline solution containing the carbonate/bicarbonate overcoated titanium electrodes separated by a semi-permeable ceramicmembrane at a current of about 6 to 9 Amps. Electrochemical treatment ofsaline is described, for example, in U.S. Pat. Nos. 7,303,660,7,828,942, and 7,897,023, which are hereby incorporated by reference.

Still other aspects of the invention provide methods of disinfecting orcleansing a mammalian tissue, such as a wound or burn, or disinfectingor cleansing a hard surface, or for treating or preserving a foodproduct or cut flowers. Due to the stability of the hypohalous acidsolutions, such methods need not be performed proximately to theproduction of the biocidal solution, and the solution may be preparedwell in advance of its use.

The solutions and formulations of the invention may be used as asterilizing, disinfecting and biocidal solution for human and animalcare. The solutions are non-hazardous, non-irritating, non-sensitizingto the skin, non-irritating to the eyes, not harmful if swallowed, andshow no evidence of mutagenic activity. For example, the method of theinvention provides for moistening, lubricating, irrigating, cleaning,deodorizing, disinfecting, or debriding a wound by rinsing, washing orimmersing the wound, with or in, the stabilized or stored hypohalousacid solutions, or by applying the solution to the wound and/or wounddressing. The wound may or may not be infected, and thus the method ofthe invention is useful for treating infected wounds and useful forpreventing infection of uninfected wounds.

In one aspect, the invention provides a convenient means for wound careand management and may be used in combination with the apparatus andmethods described in U.S. 2010/030132, which is hereby incorporated byreference in its entirety. For example, the method may comprisesupplying the stabilized solution to a wound site by one or more ofsoak, scrub, pulsed lavage, hydrosurgery, and ultrasound to effectivelydebride and disinfect a wound or tissue. The solution may be deliveredbefore, during and/or after negative pressure wound therapy to promoteproper wound healing physiology. In these embodiments, the method mayemploy a wound dressing for coordinating debridement by infusion ofhypochlorous acid with negative pressure therapy. Thus, the inventionmay be used in combination with a wound treatment apparatus and/or wounddressing.

For example, in certain embodiments, the invention allows for an initialstabilized hypochlorous acid solution soak and/or scrub to both debrideand disinfect the wound or tissue, followed by the application ofnegative pressure to the wound or tissue (as described herein) using thestabilized hypochlorous acid solution as an irrigant to control woundbioburden, remove excess exudate, and promote formation of granulationtissue. Optionally, the method also involves seamless transition to thestabilized hypohalous acid solution infusion (e.g., active or passiveinfusion without negative pressure). Such seamless transition can beeffected via a wound dressing which allows for controlled infusion ofstabilized hypochlorous acid solution with controlled vacuum source. Inthese embodiment, continued cell proliferation and regenerationcontinues without disruption of the wound bed, once the endpoints ofnegative pressure therapy have been obtained.

In certain embodiments of the invention, the wound needing care is astage I-IV pressure ulcer, stasis ulcer, diabetic ulcer, post-surgicalwound, burn, cut, abrasion, or a minor irritation of the skin. Incertain embodiments, the wound is rinsed, washed, or immersed in thesolution periodically over at least two weeks, but treatment maycontinue periodically for over about 4 weeks, about 9 weeks, or more.The wound, in some embodiments, is rinsed with the solution at leastonce a week, but may be treated with the solution at least twice a week,or more frequently.

While the hypohalous acid solution may be delivered to the wound at roomtemperature, the solution may alternatively be heated, for example, tobody temperature or about body temperature. In this embodiment, thesolution is comfortable and soothing for the patient, and is moreeffective.

In some embodiments, the invention provides a method for treating aninfected or colonized wound, tissue, surgical cavity, or bone, and amethod for reducing wound bioburden. The treatment solution inaccordance with the invention, as already described, is generallyeffective for killing or inactivating a broad spectrum of bacterial,fungal, and viral pathogens, including S. aureus, P. aeruginosa, E.coli, Enterococcus spp., C. difficile, and Candida Spp. The solutiondoes not produce resistant species, making the methods desirable overthe delivery of traditional antibiotics.

In another aspect, the solution of the invention is particularlysuitable for use in conjunction with stem cell and growth factortherapy, including the use of genetically engineered cells andengineered tissue and allografts and organs for transplant in varioustreatments. Using the stabilized hypohalous acid solution of theinvention to disinfect tissue before, during or after addition of cellsor growth factors, maintains the viability of the cells and integrity ofthe growth factors, while killing the unwanted microbes.

In certain embodiments, the solution or formulation thereof is appliedfor the control of inflammation, including an inflammatory reaction orhyper inflammation of the skin. For example, the solution or formulationthereof may be applied for use in a method as described in US2007/0196357 or US 2010/0285151, which are hereby incorporated byreference. In certain embodiments, the solution or composition of theinvention is applied (e.g., to an effected area) for treatment of apatient having a dermatoses, atopic dermatitis, skin allergy, rosasea,psoriasis, or acne, among others. In such embodiments, the HOCl solutionmay be formulated as a hydrogel, for example, as described elsewhereherein.

In certain embodiments, invention is advantageous for use againstmicrobes on surfaces because of its fast activity against bacterialspores, fungi, and other resistant microorganisms. Because of itseffectiveness and the speed at which it acts, the invention meets asubstantial public health need, and one that is not adequately addressedby current commonly-used antimicrobial agents. Accordingly, applicationof the solution to various surfaces and materials is useful to controlmicrobial contamination, not only for the care and management of wounds,but for disinfecting hard surfaces such as medical or dental equipment,preserving and decontaminating food products, water treatment, as wellas other industrial and agricultural applications. In certainembodiments, the solution or composition of the invention is applied tocrops (pre- or post-harvest) or cut flowers for their preservationand/or for improving the overall quality of the product. In someembodiments, the solution is potassium based and has one or moreutilities (e.g., methods of use) disclosed in PCT/US2011/43590), whichis hereby incorporated by reference in its entirety.

In various embodiments, including the treatment of food, agriculturalproducts, and surfaces the solution can be applied as a mist, fog,spray, or ice.

Killing, inactivating, or otherwise reducing the active population ofbacterial spores and fungi on surfaces is particularly difficult.Bacterial spores have a unique chemical composition of spore layers thatmake them more resistant than vegetative bacteria to the antimicrobialeffects of chemical and physical agents. Likewise, the unique chemicalcomposition of fungal cells, especially mold spores, makes them moreresistant to chemical and physical agents than are other microorganisms.This resistance can be particularly troublesome when the spores or fungiare located on surfaces such as food, food contact sites, ware,hospitals and veterinary facilities, surgical implements, and hospitaland surgical linens and garments.

Control of the mold Chaetomium funicola, and of bacterial spore-formingmicroorganisms of the Bacillus species, can be especially importantduring food packaging, particularly during cold or hot aseptic fillingof food and beverage products. Microorganisms of the Bacillus speciesinclude Bacillus cereus, Bacillus mycoides, Bacillus subtilis, Bacillusanthracis, and Bacillus thuringiensis. These latter microorganisms sharemany phenotypical properties, have a high level of chromosomal sequencesimilarity, and are known enterotoxin producers. Bacillus cereus is oneof the most problematic because Bacillus cereus has been identified aspossessing increased resistance to germicidal chemicals used todecontaminate environmental surfaces.

As used herein, the term “surface” refers to both hard and soft surfacesand includes, but are not limited to, tile grout, plaster, drywall,ceramic, cement, clay, bricks, stucco, plastic, wallpaper, fabric,tiles, cement, and vinyl flooring, heating and/or cooling fins, filters,vanes, baffles, vents, crevices in walls or ceilings, paper and woodproducts such as lumber, paper, and cardboard, woven products such asblankets, clothing, carpets, drapery and the like. The term surface alsoincludes human surfaces, animal surfaces, military equipment,transportation equipment, children's items, plant surfaces, seeds,outdoor surfaces, soft surfaces, air, wounds, and medical instruments,and the like.

EXAMPLES Example 1: Stabilized Hypochlorous Acid Solution

FIGS. 1A and 1B and FIGS. 2A and 2B show five cycles of AFC and pHmeasurements for hypochlorous acid wound treatment solutions as afunction of time under two environmental conditions—COLD (C) and ROOMTEMP (R). As shown, both the pH and AFC content were not stabilized overthe long term. For example, the solutions were not stabilized for morethan about one week.

In an attempt to stabilize the solution, hypochlorous acid was producedby electrochemical treatment of an electrolyte comprising 4.2 g/L NaCland 400 mg/L NaHCO₃. Samples were buffered with sodium bicarbonate(NaHCO₃) at pH 5.6, sodium bicarbonate (NaHCO₃) in combination withdisodium phosphate (Na₂HPO₄) at pH 6.7, or a mix of sodium bicarbonate(NaHCO₃), disodium phosphate and sodium diphosphate (9 NaH₂PO₄:1Na₂HPO₄)at pH 5.6. Solutions were stored in the dark for 1 month in HDPE bottlesprior to measuring AFC.

FIG. 3 shows the AFC drop as a function of time. The results show thatsolutions containing no phosphate buffer were considerably more stable(˜8% lost) when compared to Na₂HPO₄ buffered (˜25% lost) and 9NaH₂PO₄:1Na₂HPO₄ buffered solutions (˜20% lost).

The stability of the stabilized solution as a function of time wastested. Hypochlorous acid was produced by electrochemical treatment ofan electrolyte comprising 4.2 g/L NaCl and 400 mg/L NaHCO₃. The solutionhad a pH of 5.3, an alkalinity of zero (0), and approximately 250 ppm ofAFC. This solution was packaged in HDPE bottles and stored in the dark.The biocidal activity and stability of the solution as a function oftime was tested by measuring pH and AFC content in unopened test bottlesover a period of greater than 390 days. The results are shown in FIG. 4,showing that the solutions are stabilized, with regard to AFC contentand pH for over one year.

Generally, it is assumed by NaOCl manufacturers that sodium hypochloritesolution loses approximately 20% of its titrable chlorine in the first 6months and up to 60% within a year. One study determined that it wouldtake 166 days for a solution of 25 mg/mL sodium hypochlorite solution at20° C. to reach 20 mg/mL of free residual chlorine based on stabilitystudies conducted at 50° C. and 70° C. and calculations with theArrhenius Equation (See Nicoletti et al., “Shelf-Life of a 2.5% SodiumHypochlorite Solution as Determined by Arrhenius Equation,” Braz Dent J(2009) 20(1): 27-31). Other studies have shown similar results (See“Product Characteristics, Sodium Hypochlorite-Stability PCH-1400-0007”PCH-1400-0007-W-EN (WW), Issue 1—May 2005, Published by Solvay ChemicalsInternational SA). Contrary to these assumptions, the NaHCO₃ bufferedhypochlorous acid solution of the claimed invention retained greaterthan 75% of the initial level of titrable chlorine along with a pH shiftof less than one unit over a period of one year.

Example 2: Biocidal Activity of Stabilized HOCl Solution

Three solutions comprising different concentrations of hypochlorous acidwere produced. The first solution, containing 250 ppm hypochlorous acid,was produced via electrochemical treatment of an electrolyte comprising4.2 g/L NaCl and 400 mg/L NaHCO₃. The second solution, similarlyproduced via electrochemical treatment, contained 480 ppm hypochlorousacid, but no NaHCO₃. The final solution contained 480 ppm hypochlorousacid, but in addition, incorporated 1000 mg/L NaHCO₃.

To simulate a worst-case scenario, spores of C. difficile, a bacterialstrain with high antibiotic resistance, were suspended in a highlyconcentrated organic medium, consisting of homogenized skin cells frompig, mucin, and bovine serum albumin. After suspending themicroorganisms in the organic solution, they were inoculated ontoplastic carriers, allowed to desiccate and exposed to each solution induplicate for either 0, 4, 6, 8, 10 or 30 minutes. Due to the fact thatnone of the existing disinfectants have stood up to this organic load(including bleach), two different concentrations of hypochlorous acidwere tested.

The results (FIG. 5) demonstrate that the solution with sodiumbicarbonate possesses higher biocidal activity against C. difficilespores under high organic load conditions.

Example 3: Extended Stability Study

FIG. 6 shows the results of an extended stability study of HOCl producedby electrochemical treatment of NaHCO₃ enriched NaCl solution attargeted pH 5.4, bottled in a polyethylene terephthalate (PET) containerand stored at room temperature. The molar content of NaHCO₃ isequivalent to 1 mole NaHCO₃ per 1 mole HOCl in this formulation. Everysecond month 4 new samples of HOCl stabilized solution were opened overthe storage time, and then reopened one month later and tested on aweekly basis. Comparison of the pH and AFC of the first opened samplewith the last opened, weekly opened during that month, confirmed thestability of HOCl stabilized with sodium bicarbonate.

Example 4: Stability of HOCl with Added Sodium Bicarbonate

The stability of HOCl added to containers comprising dry sodiumbicarbonate is shown in FIGS. 7A and 7B. The ionic strength or solutionsalinity was not affected by the addition of sodium bicarbonate. Theresults demonstrate that bicarbonate as a stabilizer affects both the pHand AFC stability. Without being bound to any theory, in cases where thepH is about 5.5 and the buffering ability of bicarbonate is minimal,bicarbonate may act as a stabilizer, in part, by scavenging freeradicals generated by the dissociation of hypochlorous acid. The resultis a minimal drop in pH and AFC over time.

Example 5: Stability of HOCl Composition for Agricultural Applications

The effect of DIC content on pH and solution stability in hypochlorousacid solutions electrochemically generated, and additionally bufferedwith di- and monosodium phosphate for targeted pH (which have utilityfor agricultural applications), is shown in FIG. 8. Compositions ofhypochlorous acid with phosphate additives were tested with and withoutbicarbonate. The results showed better stability of hypochlorous acid inthe presence of bicarbonate than with phosphates alone. Combination ofDIC and phosphate buffers provided better solution stability withoutsignificantly increasing the total dissolved solids content.

Example 6: Hydrogel Formulations

A hydrogel formulation containing the stabilized hypochlorous acidsolution was developed. The use of bicarbonate or dissolved inorganiccarbon in accordance with the invention has only a minimal effect on theionic strength or electroconductivity of the solution. Thus, in additionto stabilizing a HOCl solution in the pH range of about 4 to about 7.5(e.g. about 6.0), bicarbonate or carbonate do not affect the ionicstrength at the targeted pH, making it possible to use hypochlorous acidwith more than 200 ppm of available free chlorine as the dispersingmedia in a gel formulation, especially where low ionic strength iscritical for the formulation.

A low ionic strength hypochlorous acid solution (conductivity ≤mS/cm(i.e., millisiemens per centimeter)), AFC=300 ppm, pH 5.3 was used for ahydrogel formulation containing 3% sodium magnesium fluorosilicate. Morethan 4% sodium magnesium fluorosilicate was required for the productionof a hydrogel of equal viscosity made out of 8 mS/cm of HOCl with equalpH and AFC content. A lower ionic strength HOCl solution as a dispersingmedia allows for the addition of other buffering agents for pHoptimization in the final product without negative effects on physicalappearance and product stability. Due to the fact that the gelling agentis a dry buffer itself, the ability to add other buffers for pHoptimization in a final product can be beneficial.

In another example, hypochlorous acid solution, AFC 350 ppm, pH 5.3,salinity 4 g/l (conductivity 8 mS/cm) was used for the production of ahydrogel containing 4% F₁₂MgNa₂Si₂ (sodium magnesium fluorosilicate).The hydrogel produced had a viscosity of 330 centipoises (cP) and a pHof 8.2. To bring the pH to a “skin-friendly” range phosphoric acid wasadded as a buffering agent. The final hydrogel had a shift in pH overtime from pH 6 to 6.8 as seen in FIG. 9. Additional buffer is limited bygel viscosity as it shifts to 220 cP with a conductivity increase to 10mS/cm.

Low ionic strength hypochlorous acid, AFC=370 ppm, was produced byelectrochemical treatment of sodium chloride substantially as describedin U.S. Pat. No. 7,897,023 (which is hereby incorporated by reference inits entirety), and collected in a container with dry sodium bicarbonate,equivalent to 500 ppm of NaHCO₃ as an initial form of dissolvedinorganic carbon (DIC). An HOCl pH 5.2 and conductivity 0.8 mS/cmproduced by this process was and used as dispersing media for a gelpreparation. 3% of sodium magnesium fluorosilicate was used as a gellingagent. Hydrogel formed with a viscosity of about 10,000 cP in less than25 minutes with an initial pH of 8.4 and a conductivity of about 1mS/cm. Phosphoric acid was added in the amount of less than 0.25% tobring the pH of the hydrogel down to a skin-friendly range (about pH5.5-5.8). A hydrogel with a viscosity above 2,000 cP was formed.

All references cited herein are incorporated by reference in theirentireties.

What is claimed is:
 1. A stabilized hypobromous acid (HOBr) solutionconsisting of: a solution prepared by electrolysis of a solutionconsisting of water, a bromide salt, and optionally dissolved inorganiccarbon (DIC) in the form of bicarbonate or carbonate of alkali oralkaline earth metals, and a stabilizing amount of DIC in the form ofbicarbonate or carbonate of alkali or alkaline earth metals, wherein anavailable free bromine (AFB) content of the solution is from about 10 toabout 5,000 parts per million (ppm), wherein the pH of the solution isfrom 4.0 to 7.5, and wherein a ratio of the stabilizing amount of theDIC to the AFB content is at least 1:2.
 2. The solution of claim 1,wherein the AFB content and the pH of the solution are stable for atleast 6 months.
 3. The solution of claim 1, wherein the AFB content isfrom about 100 to about 1,000 ppm, from about 100 to about 500 ppm, orfrom about 150 to about 250 ppm.
 4. The solution of claim 1, wherein thepH is from 5.0 to 7.0.
 5. The solution of claim 1, wherein the pH isfrom 5.0 to 6.4.
 6. The solution of claim 1, wherein the DIC is sodiumbicarbonate.
 7. The solution of claim 1, wherein the stabilized solutionhas an AFB content of from 100 ppm to 500 ppm and from 300 mg/L to 1000mg/L of sodium bicarbonate.
 8. A method for disinfecting or cleansing amammalian tissue, comprising applying the solution of claim 1 to themammalian tissue.
 9. The method of claim 8, wherein the mammalian tissueis infected, has a wound or a burn, has a dermatosis, or has atopicdermatitis.
 10. A method for disinfecting or cleansing a hard surface,comprising applying the solution of claim 1 to the hard surface.
 11. Themethod of claim 10, wherein the hard surface comprises porcelain, steel,iron, or ceramic material.
 12. A method for preserving ordecontaminating food products, comprising applying the solution of claim1 to a food product.
 13. A method for controlling microbialcontamination of water, comprising applying the solution of claim 1 towater in need of treatment or control for microbial contamination.